Para-phenylene sulfide block copolymers, process for the production of the same and use thereof

ABSTRACT

A para-phenylene sulfide block copolymer consisting essentially of a recurring unit (A) ##STR1## and a recurring unit (B) ##STR2## said recurring units (A) being present in the form of a block of 20 to 5,000 units of (A) on the average in the molecular chain, the mol fraction of the recurring units (A) being in the range of 0.50 to 0.98, the block copolymer having a melt viscosity (η*) of 50 to 100,000 poise as determined at 310° C. at a shear rate of 200 sec -1  and having: (a) a glass transition temperature (Tg) of 20° to 80° C., (b) a crystalline melting point (Tm) of 250° to 285° C., and (c) a crystallization index (Ci) of 15 to 45, this value being that of the heat-treated, but not stretch-oriented copolymer, which block copolymer is preferably produced by a process comprising a first step of heating an aprotic polar organic solvent containing a dihaloaromatic compound consisting essentially of a m-dihalobenzene and an alkali metal sulfide to form a reaction liquid (e) containing a m-phenylene sulfide polymer consisting essentially of recurring units (B) ##STR3## and a second step of adding a p-dihalobenzene to the reaction liquid (E) and heating the mixture in the presence of an alkali metal sulfide an an aprotic polar organic solvent to form a block copolymer consisting essentially of the recurring units (B) and recurring units (A) ##STR4##

This is a Rule 60 divisional application of Ser. No. 858,851, filed Apr.30, 1986 which is a continuation-in-part of Ser. No. 748,464, filed June25, 1985, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Art

The present invention relates to a p-phenylene sulfide copolymer. Moreparticularly, the invention relates to a crystalline p-phenylene sulfideblock copolymer comprising a block of p-phenylene sulfide recurringunits ##STR5## in the molecular chain.

2. Prior Art

Concerning p-phenylene sulfide polymers, there have been numerousreports on p-phenylene sulfide homopolymers (as disclosed in thespecifications of Japanese Patent Publications Nos. 12240/1977 and3368/1970 and Japanese Patent Laid-Open No. 22926/1984). Also, somereports can be found on p-phenylene sulfide random copolymers (asdescribed, for example, in the specification of U.S. Pat. No.3,869,434).

The p-phenylene sulfide homopolymers have been used as heat-resistantthermoplastic resins mainly in injection molding processes since thehighly crystalline p-phenylene sulfide homopolymers can be used at atemperature as high as nearly their crystalline melting point (about285° C.) when they are highly crystallized. However, these polymers havebeen accompanied by the problems of excessively high crystallizationrate in the melt process and ready formation of rough spherulites. Thatis, when films are to be formed from them by an inflation method, theyare crystallized and solidifed prior to sufficient inflation, whereby itis difficult to form intended stretched and oriented films. In extrusionmolding by means of a T-die to form a sheet, the crystallization andsolidifying occur prior to the winding of the sheet around a wind-uproll, whereby it is difficult to obtain a smooth sheet having a uniformthickness. In melt extrusion to form pipes, rough spherulites are formedprior to the quench to make it difficult to obtain the tough extrusionmoldings. In melt coating of electric wires, rough spherulites areformed in the coating film to make it difficult to obtain tough coatingfilms. In the production of fibers by melt spinning process, thecrystallization and solidifying proceed in the course of the meltspinning operation to make sufficient stretch and orientationimpossible, and, therefore, tough fibers cannot easily be obtained.

While the p-phenylene sulfide random copolymers, which are generallynon-crystalline, have a characteristic feature of being melt-processedquite easily, since they are not crystallized or solidified in thecourse of the melt spinning operation, they are problematic in thattheir heat resistance is extremely poor due to thenon-crystallizability.

Printed circuit boards composed of an insulating base and a metal layerof a circuit pattern formed on the surface thereof have been used widelyin the field of electronic appliances.

As the insulating materials for the printed circuit boards, compositesof thermosetting resins, such as epoxy, phenolic and unsaturatedpolyester resins, with fibrous reinforcing materials, such as glassfibers, synthetic fibers and paper, have been mainly used. However,these materials are problematic in that a long time is necessary forrecovery of the solvent and curing of the resin and in that they have ahigh hygroscopicity and only a poor resistance to CAF (conductive anodicfiber growth).

Recently, attempts were made to use a composite of poly-p-phenylenesulfide which is a thermoplastic resin and a fibrous reinforcingmaterial for the production of insulating bases for printed circuitboards (as described in the specifications of Japanese Patent Laid-OpenNos. 96588/1982 and 3991/1984). However, the insulating base comprisingthe poly-p-phenylene sulfide has insufficient adhesion to the metallayer, and, therefore, the metal layer is easily peeled off.

Electronic components such as IC, transistors, diodes and capacitorshave been sealed with or encapsulated within a synthetic resin orceramic substance for the purposes of preventing changes in theproperties due to the external atmosphere, preventing deformation, andmaintaining the electrical insulating property.

The sealing resins used heretofore include thermosetting resins,particularly, epoxy and silicone resins. However, these resins have thefollowing defects: (1) the molding time is prolonged, since a long timeis necessary for the thermosetting, (2) a long post-curing time isrequired, (3) as the molding shot number is increased, contamination ofthe mold accumulates, (4) the resin is easily deteriorated duringstorage and (5) unnecessary portions like runner gates of the moldingscannot be reused.

For overcoming the above mentioned drawbacks, processes whereinpoly-p-phenylene sulfide (a thermoplastic resin) is used have beenproposed (as described, for example, in the specifications of JapanesePatent Publication No. 2790/1981 and Japanese Patent Laid-Open Nos.22363/1978, 81957/1981, 20910/1984 and 20911/1984).

When poly-p-phenylene sulfide is used, the sealing or encapsulation isconducted ordinarily by a melt molding process. In this process, thecrystallization proceeds rapidly to form rough spherulites in the stepof solidifying the molten resin. Therefore, a marked molding shrinkageoccurs in the resin layer, particularly around the spherulites, to formcracks in the resin layer, to cut or to deform the bonding wire, and toform a gap between the lead frame or bonding wire and the resin layer.As a result, a problem arises in the resulting electronic parts in thewater penetrates thereinto through the interface between the resin layerand the lead frame or bonding wire to cause deterioration of the qualityof the electronic parts particularly at a high temperature in a highlyhumidity atmosphere. To solve these problems, processes whereininorganic fillers or various additives are used have been proposed.However, the problems cannot be solved essentially unless the propertiesof the base resin are altered.

SUMMARY OF THE INVENTION

According to the present invention, the problems of excessively highcrystallization rate and rough spherulite-forming property of thep-phenylene sulfide homopolymers and also non-crystallizability and poorheat resistance of the p-phenylene sulfide random copolymers are solved.The present invention provides a phenylene sulfide polymer havingexcellent crystallinity, heat resistance and easy melt-processability.That is, the present invention provides a crystalline phenylene sulfidepolymer suitable particularly for the inflation film-forming process,melt extrusion molding, electric wire coating, melt spinning andstretching.

The phenylene sulfide polymer according to the present invention is apara-phenylene sulfide block copolymer consisting essentially ofrecurring units (A) ##STR6## and recurring unit (B) ##STR7## saidrecurring units (A) being present in the form of a block of 20 to 5,000units thereof on the average in the molecular chain, characterized inthat the mol fraction of the recurring units (A) is in the range of 0.50to 0.98, and the copolymer has a melt viscosity (η*) of 50 to 100,000poise, which is hereinbelow indicated as P, as determined at 310° C. ata shear rate of 200 sec⁻¹ and physical properties which will bedescribed hereinafter.

According to this invention in another aspect thereof, there is provideda process for producing the p-phenylene sulfide block copolymerdescribed above which process comprises a first step of heating anaprotic polar organic solvent containing a p-dihalobenzene and an alkalimetal sulfide to form a reaction liquid mixture (C) containing ap-phenylene sulfide polymer consisting essentially of recurring units(A) ##STR8## and a second step of adding a dihaloaromatic compoundconsisting essentially of a m-dihalobenzene to the reaction liquidmixture (C) and heating the mixture in the presence of an alkali metalsulfide and an aprotic polar organic solvent to form a block copolymerconsisting essentially of a block consisting essentially of therecurring units (A) and a block consisting essentially of recurringunits (B) ##STR9## wherein: the reaction in the first step is carriedout until the degree of polymerization of the recurring units (A) hasbecome 20 to 5,000 on the average; the reaction in the second step iscarried out until the mol fraction (X) of the recurring units (A) in theresulting block copolymer has become 0.50 to 0.98; and the reactions inthese steps are carried out so that the resulting p-phenylene sulfideblock copolymer will have a melt viscosity (η*) measured underconditions of 310° C./200 sec⁻¹ of 50 to 100,000 P and physicalproperties which will be described hereinafter.

Another mode of practice of the process of the present invention forproducing the p-phenylene sulfide block copolymer described abovecomprises a first step of heating an aprotic polar organic solventcontaining a dihaloaromatic compound consisting essentially of am-dihalobenzene and an alkali metal sulfide to form a reaction liquidmixture (E) containing a m-phenylene sulfide polymer consistingessentially of recurring units (B) ##STR10## and a second step of addinga p-dihalobenzene to the reaction liquid (E) and heating the mixture inthe presence of an alkali metal sulfide and an aprotic polar organicsolvent to form a block copolymer consisting essentially of therecurring units (B) and recurring units (A) ##STR11## wherein: thereaction in the first step is carried out until the average degree ofpolymerization of at least 2 and in the range of ##EQU1## where Xrepresents a mol fraction of the recurring units (A) in the resultingblock copolymer which is in the range of 0.50 to 0.98 has been obtained;the reaction in the second step is carried out until the mol fraction(X) of the recurring units (A) in the resulting block copolymer hasbecome 0.50 to 0.98; and the reactions in these steps are carried out sothat the resulting p-phenylene sulfide block copolymer will have a meltviscosity (η*) measured under conditions of 310° C./200 sec⁻¹ of 50 to100,000 P and physical properties which will be described hereinafter.

Still another mode of practice of the process of the present inventionfor producing the p-phenylene sulfide block copolymer described abovecomprises a first step of heating an aprotic polar organic solventcontaining a p-dihalobenzene and an alkali metal sulfide to form areaction liquid (C) containing a p-phenylene sulfide polymer comprisingrecurring units (A) ##STR12## a second step of heating the aprotic polarorganic solvent containing a dihaloaromatic compound consistingessentially of a m-dihalobenzene and an alkali metal sulfide to form areaction liquid (D) containing a m-phenylene sulfide polymer consistingessentially of recurring units (B) ##STR13## and a third step of mixingthe reaction liquids (C) and (E) obtained as above and heating themixture to form a p-phenylene sulfide block copolymer consistingessentially of blocks of said recurring units (A) and the recurringunits (B), wherein: the reaction in the first step is carried out untilthe average degree of polymerization of 20 to 5,000 recurring units (A)on the average has been obtained; the reaction in the second step iscarried out until the average degree of polymerization of at least 2 andin the range of ##EQU2## wherein X represents a mol fraction of therecurring units (A) in the resulting block copolymer which is in therange of 0.50 to 0.98 has been obtained; the reaction in the third stepis carried out so that the mol fraction (X) of the recurring units (A)in the resulting block copolymer will be in the range of 0.50 to 0.98;and the reactions in these steps are carried out so that the resultingp-phenylene sulfide block copolymer will have a melt viscosity (η*)measured under conditions of 310° C./200 sec⁻¹ of 50 to 100,000 P andphysical properties which will be described hereinafter.

The above described p-phenylene sulfide block copolymer has thefollowing physical properties:

(a) a glass transition temperature (Tg) of 20° to 80° C.,

(b) a crystalline melting point (Tm) of 200° to 350° C., and

(c) a crystallization index (Ci) of 15 to 45, this value being that ofthe heat-treated, but not stretch-oriented copolymer.

The present invention in still another aspect thereof also providesmolded articles of the above described p-phenylene sulfide blockcopolymer.

The present invention further relates to the use of the block copolymerfor the production of a printed circuit board.

The printed circuit board according to the present invention is composedof an insulating base which is a molded plate comprising a composite of50 to 95 vol. % of a polymer comprising mainly a phenylene sulfide blockcopolymer and 5 to 50 vol. % of a fibrous reinforcing material and ametal layer of a circuit pattern formed on the surface of the base, saidphenylene sulfide block copolymer comprising 20 to 5,000 recurring units##STR14## on the average in the molecular chain, said recurring units##STR15## having a mol fraction of 0.50 to 0.98 and said copolymerhaving a melt viscosity (η*) of 300 to 50,000 P as determined at 310° C.at a shear rate of 200 sec⁻¹ and a crystalline melting point of 200° to350° C.

The present invention in a further aspect thereof provides methods ofuse of the above-mentioned block copolymer as a starting material for acomposition for sealing or encapsulating electronic parts.

The composition of the invention for sealing electronic parts comprises100 parts by weight of a synthetic resin component and 20 to 300 partsby weight of an inorganic filler, characterized in that the syntheticresin component comprises mainly a phenylene sulfide block copolymerconsisting essentially of recurring units ##STR16## and recurring units##STR17## wherein the former recurring units form a block having anaverage degree of polymerization of 20 to 2000 bonded in the molecularchain and have a mol fraction in the range of 0.50 to 0.95, saidcopolymer having a melt viscosity of 10 to 1500 P as determined at 310°C. and at a shear rate of 200 sec⁻¹.

A process for sealing or encapsulating electronic parts is alsopresented according to the present invention, which process ischaracterized in that the electronic parts are sealed by an injectionmolding method with a sealing composition comprising 100 parts by weightof a synthetic resin component and 20 to 300 parts by weight of aninorganic filler wherein the synthetic resin component comprises mainlya phenylene sulfide block copolymer consisting essentially of recurringunits ##STR18## and recurring units ##STR19## in which the formerrecurring units form a block having an average degree of polymerizationof 20 to 2,000 bonded in the molecular chain and have a mol fraction inthe range of 0.50 to 0.95, said copolymer having a melt viscosity of 10to 1,500 P (310° C., shear rate: 200 sec⁻¹).

According to the block copolymers of the present invention, the problemsof the melt processability of p-phenylene sulfide homopolymer can besolved while the crystallizability and heat resistance of the latter aremaintained. The copolymers of the present invention have a greatcharacteristic processability whereby they can well be molded in atemperature zone ranging from the crystalline melting point (Tm) to thecrystallization temperature on the higher temperature side (Tc₂) (i.e.,the temperature at which the crystallization begins as the temperatureis lowered gradually from the molten state), i.e., in the supercoolingregion. Therefore, the copolymers of the invention are suitable forinflation molding, extrusion molding (production of sheets, pipes,profiles, etc.), melt spinning and electric wire coating. Othercharacteristic physical properties will be described below.

The phenylene sulfide block copolymers used as the base resin in thepresent invention are free of the afore-described problems of thephenylene sulfide homopolymer, while retaining substantially thedesirable characteristics of the cyrstalline homopolymer. The copolymershave a high adhesion to metal layers.

Therefore, a printed circuit board comprising a plate formed by moldinga composite of the phenylene sulfide block copolymer of the presentinvention (base resin) and a fibrous reinforcing material and a metallayer formed on the surface of the plate is advantageous in that themetal layer has good adhesion to the insulating base even when the layeris formed by an additive method and in that it has also excellentinsulating properties and resistance to soldering heat. Thus, theprinted circuit board can be used widely in the field of electronicdevices and appliances.

The phenylene sulfide block copolymers used as the base resin in thepresent invention are free of the afore-described problems of thephenylene sulfide homopolymer, which retaining substantially thedesirable characteristics of the crystalline homopolymer. Thus, thesecopolymers are suitable for sealing electronic components.

DETAILED DESCRIPTION OF THE INVENTION Block Copolymers Chemicalstructure of the copolymer

The crystalline p-phenylene sulfide block copolymer according to thepresent invention is a high molecular substance having such a chemicalstructure that the recurring units (A) ##STR20## in the form of blocksare contained in the molecular chain.

According to our findings, it is necessary that the p-phenylene sulfiderecurring units (A) be distributed in the moleculwar chain in the formof a block comprising 20 to 5,000, preferably 40 to 3,500, andparticularly 100 to 2,000 units, on the average, so that the copolymercan be processed easily in the inflation film-forming, melt-extrusionmolding, electric wire coating, melt spinning and stretching processeswhile high heat resistance due to the crystallinity of the p-phenylenesulfide homopolymer is maintained. Copolymers wherein the recurringunits (A) are distributed at random or wherein a block comprising up to20 recurring units (A) on the average are distributed are not preferredsince the crystallinity as that of the p-phenylene sulfide homopolymeris lost completely or partially, and the heat resistance due to thecrystallinity is lost. On the other hand, when the recurring units (A)are distributed in the form of blocks comprising more than 5,000 units(A) on the average, the resulting copolymer undesirably hassubstantially the same properties as those of the p-phenylene sulfidehomopolymer.

It is necessary that the mol fraction X of the recurring units (A) inthe blocks in the copolymer molecular chain be in the range of 0.50 to0.98, preferably in the range of 0.60 to 0.90. When the mol fraction ofthe p-phenylene sulfide recurring units is controlled in this range, theresulting copolymer has excellent processability in the steps ofinflation-film formation, melt extrusion, electric wire coating and meltspinning and drawing while retaining the excellent crystallinity andheat resistance peculiar to the p-phenylene sulfide homopolymer. Whenthe mol fraction of the recurring units (A) exceeds 0.98, the effect ofimproving the processability becomes insufficient. On the other hand,when it is less than 0.5, the crystallinity is reduced, and,accordingly, the heat resistance is seriously reduced. The mol fractioncan be controlled easily by varying the proportion of the startingmaterials used in the polymerization step.

The recurring units (B) which constitute the block copolymer of thepresent invention together with the p-phenylene sulfide recurring units(A) are arylene sulfide units --Ar--S-- consisting essentially ofm-phenylene sulfide recurring units ##STR21## In this formula, Arrepresents an aromatic compound residue. --Ar-S-- units other than them-phenylene sulfide recurring units include: ##STR22## Two or more ofthese recurring units can be used together. The term "consistingessentially of m-phenylene sulfide units B" used herein indicates thatthe amount of m-phenylene sulfide units is at least 80 molar %,preferably 90 to 100 molar %, based on the total recurring units (B).

The degree of polymerization of the p-phenylene sulfide block copolymeraccording to the present invention represented in terms of meltviscosity η* is 50 to 100,000 P, preferably 1,000 to 50,000 P. The meltviscosity η* is determined by means of a Koka-shiki flow tester at 310°C. and at a shear rate of 200 sec⁻¹. When the value of η* is less than50 P, the intended tough molded article cannot be obtained, and when itexceeds 100,000 P, the molding operation becomes difficult.

The number of the recurring units (A) ##STR23## in the block copolymeraccording to the present invention, i.e., the degree of polymerizationof the poly-p-phenylene sulfide block, can be determined by afluorescent X-ray method. The degree of polymerization of thepoly-m-phenylene sulfide block components (B) can be measured by gelpermeation chromatography (GPC). The mol fraction (X) of thepoly-p-phenylene sulfide block components can be determined easily by aninfrared analysis.

Physical properties

The p-phenylene sulfide block copolymer of the present invention has aglass transition temperature (Tg) of 20° to 80° C., a crystallinemelting point (Tm) of 200° to 350° C. and a crystallization index (Ci)of 15 to 45 (this value being of the heat treated, but non-stretchednon-oriented copolymer sheet).

The block copolymer of the present invention has a Tg lower than that ofthe p-phenylene sulfide homopolymer. Therefore, this copolymer isadvantageous in that the stretching temperature can be lowered and theprocessing can be conducted under conditions substantially the same asthose employed in processing polyethylene terephthalate (PET), etc.

Although the Tg of the block copolymer of the present invention is lowerthan that of the homopolymer, this copolymer is characterized in that itis a crystalline polymer having a Tm close to the Tm of the homopolymerprobably because the heat resistance of the polymer is governed by the##STR24## blocks. This is the most remarkable difference between thecopolymer of the present invention and an ordinary p-phenylene sulfidecopolymer (i.e., random copolymer), since the Tm of the latterdisappears (i.e., the latter becomes amorphous) or it is greatlyreduced. Thus, the heat resistance of the copolymer of the presentinvention can be maintained.

The difference between the upper limit Tc₂ of the crystallizationtemperature range (i.e., the temperature at which the crystallization isinitiated as the temperature of the molten block copolymer is lowered)of the block copolymer of the present invention and the Tm thereof isquite large, and the crystallization rate is not very high, while Tc₂ ofthe p-phenylene sulfide homopolymer is very close to the Tm thereof andthe crystallization rate of this homopolymer is quite high. These areimportant characteristic features of the block copolymer of the presentinvention. As described above, the block copolymer of the presentinvention is suitable for various processing processes since it can beamply molded even in the supercooling temperature range, i.e., thetemperature range between Tm and Tc₂, while the homopolymer cannot bemelt-processed easily in the inflation, extrusion molding or meltspinning process, since the Tc₂ thereof is very close to the Tm thereof,and its crystallization rate is quite high, whereby it is crystallizedrapidly after the melt spinning.

The block copolymer of the present invention has a Tc₂ in the range ofordinarily 150° to 230° C. The lower limit Tc₁ of the crystallizationtemperature range (i.e., the temperature at which the crystallization isinitiated as the temperature of the amorphous block copolymer iselevated) of the block copolymer of the present invention is ordinarilyin the range of 100° to 150° C.

The values of Tm, Tg, Tc₁ and Tc₂ are values represented by the meltingpeak, the temperature at which the heat absorption is initiated, and thecrystallization peak, respectively, as measured by using 10 mg of asample by means of a differential scanning calorimeter (DSC) of ShimadzuSeisaku-sho at a temperature-elevation or -lowering rate of 10° C./minin a nitrogen atmosphere. This sample is in molten state to rapidlycooled, substantially amorphous state.

The degree of crystallinity of the block copolymer of the presentinvention is ample for maintaining the heat resistance due to thecrystallization of the polymer though it does not exceed the degree ofcrystallinity of the p-phenylene sulfide polymer. Therefore, high heatresistance of the copolymer can be obtained by amply crystallizing thesame according to heat setting. Further, the heat resistance can beimproved by increasing the degree of crystallinity by carrying outstretch-orientation prior to the heat setting. Ordinary randomcopolymers have no crystallinity whatsoever or they have only a slightcrystallinity, and, therefore, the effect of realizing heat resistanceby heat setting cannot be expected. They have lost their property ofheat resistance.

The crystallization index (Ci) of the heat-treated, but notstretch-oriented, block copolymer of the present invention is in therange of 15 to 45. The crystallization index Ci is a value obtained froman X-ray diffraction pattern (2θ=17°-23°) according to the formula:

    Ci=[Ac/(Ac+Aa)]×100

wherein Ac represents crystalline scattering intensity and Aa representsamorphous scattering intensity [ref.: J. Appl. Poly. Sci. 20, 2545(1976)]. The value Ci is determined in the present invention bymelt-pressing the block copolymer at a temperature higher than itsmelting point by about 30° C. by means of a hot press, rapidly coolingthe same with water to obtain a film having a thickness of 0.1 to 0.2mm, heat-treating the film at a temperature lower than the melting pointby 20° C. for 20 min. to effect the crystallization, and measuring theCi of the thus heat-treated film. The heat-treated film has an increasedCi in the range of generally 40 to 90 after the stretch-orientation.

Since the homopolymer has an excessively high crystallization rate, and,accordingly, coarse spherulites are formed, rapid crystallization andsolidifying occur after the melt molding, whereby stretch orientationthereof by ample expansion of the same by the inflation method isdifficult. It is quite difficult to prepare a smooth, uniform sheet orfilm by a T-die method, to obtain highly stretchable filaments by amelt-spinning method, or to obtain tough extrusion-molded products ortough electric wire coatings from the homopolymer for the same reasonsas described above.

On the other hand, when the block copolymer of the present invention isused, it is possible to obtain an amply expanded and stretch-orientedfilm or sheet by the inflation method, since said block copolymer has asuitable crystallization rate, and, therefore, the resulting spherulitesare fine. Thus, it becomes possible to prepare a smooth, uniform sheetor film by a T-die method, to obtain tough moldings by an extrusionmethod, to obtain highly stretchable filaments by a melt-spinningprocess and to obtain a tough electric wire coating.

In this connection, it is very difficult to obtain a practicallyvaluable, heat set film from a homopolymer having a melt viscosity η* ofas low as 2,000 P, since it is partially whitened due to the coarsecrystal formation in the heat setting. On the other hand, a practicallyvaluable, uniform, heat set film can be obtained from the block polymerof the present invention since coarse spherulites are not easily formed.Because the formed spherulites are not easily made coarse, not onlyfilms but also other molded articles obtained from the block copolymerof the present invention have greatly advantageous physical properties,whereby they are not made brittle but keep their toughness even afterthe heat setting carried out for the purpose of imparting the heatresistance.

Production of Block Copolymer Summary

The block copolymer of the present invention consists essentially of ablock consisting essentially of p-phenylene sulfide recurring units (A)and a block consisting essentially of recurring units (B) consistingessentially of m-phenylene sulfide. This copolymer can be produced byany process capable of forming both blocks and bonding them.

More specifically, in one mode of the process, one of the blocks isformed, and the polymer chain is then extended by polymerizationthereover of the monomer to form the other block whereby formation ofthe second block and bonding of the second block with the first blocktake place simultaneously.

The process for producing the block copolymer of the present inventionis essentially the same as a conventional process for producing aphenylene sulfide polymer except that care is taken in the formation andbonding of the blocks and the varieties of the phenylene sulfiderecurring units and that modifications are made if necessary in theformer process. That is, the process of the present invention forproducing the block polymer comprises heating an alkali metal sulfideand a dihaloaromatic compound (comprising mainly p- andm-dihalobenzenes) in an aprotic polar organic solvent to accomplishcondensation (to remove the alkali metal halide).

Starting materials

The alkali metal sulfides which are the sources of the sulfide bond arepreferably Na, Li, K and Rb sulfides. From the viewpoint of reactivity,Na and Li sulfides are particularly preferred. When they contain waterof crystallization, the water content thereof can be reduced suitably bydistillation or drying prior to the initiation of the polymerizationreaction.

Preferred examples of the aprotic polar organic solvents used as thereaction medium are carboxylic acid amides, organic phosphoric acidamides, and urea derivatives. Among these, N-methylpyrrolidone, which ishereinbelow abbreviated as "NMP", hexatrimethylphosphoric acid triamideand tetramethylurea are particularly preferred from the viewpoints ofchemical and thermal stabilities.

Among the dihaloaromatic compounds, examples of p-dihalobenzenes usedfor forming the p-phenylene sulfide blocks are p-dichlorobenzene andp-dibromobenzene. Preferred examples of the dihalo-substituted aromaticcompounds usable in a small amount together with the m-dihalobenzene toform the other blocks include the following compounds, (but they are notlimited to these compounds): ##STR25## wherein X and Y each represent ahalogen atom.

Further, polyfunctional compounds having 3 or more halogen atoms such as1,2,3- or 1,2,4-trihalobenzenes can also be used.

As a matter of course, the polymerization conditions must be selected soas to obtain a polymer having a η* of 50 to 100,000 P, preferably 1,000to 50,000 P.

Production process (I)

Production process (I) comprises forming blocks of the p-phenylenesulfide recurring units (A), and then forming recurring units consistingessentially of m-phenylene sulfide in situ with simultaneous bonding ofit with the block (A).

When the starting alkali metal sulfide contains water ofcrystallization, that is, when the starting alkali metal sulfide is Na₂S.9H₂ O, Na₂ S.5H₂ O or Na₂ S.3H₂ O (including a product of in situreaction of NaHS.2H₂ O+NaOH→Na₂ S.3H₂ O), it is preferable to reduce thewater content thereof suitably by drying before it is added to theorganic solvent, to add the alkali metal sulfide alone to the organicsolvent, and then to heat the mixture to about 200° C. to distill thewater off or to chemically dehydrate the same by addition of CaO, etc.so as to control the water content suitably (ordinarily to 0.5 to 2.5mol/mol of the sulfide). Then, p-dihalobenzene is added in such anamount that the molar ratio thereof to the sulfide will ordinarily be0.95 to 1.05. The mixture is heated to a suitable temperature,preferably 160° to 300° C., particularly 190° to 260° C., to carry outthe polymerization reaction until an average polymerization degree ofthe resulting p-phenylene sulfide prepolymer of 20 to 5,000 is obtainedto obtain the reaction liquid mixture (C) containing the prepolymer.

The required time is generally about 0.5 to 30 hrs.

On the other hand, the starting alkali metal sulfide is dried and thencharged into the organic solvent in the same manner as above, or,alternatively, the water content of the alkali metal sulfide iscontrolled by distillation in the organic solvent or by a chemicaldehydration, and then a m-dihalobenzene (which can contain a smallamount of a dihalo-substituted aromatic compound) is added theretousually in such a amount that the molar ratio thereof to the sulfidewould be 0.95/1 to 1.05/1 to obtain an unreacted liquid mixture (D).

The unreacted liquid mixture (D) is mixed with the reaction liquidmixture (C) containing the prepolymer in a given ratio (i.e., such aratio that the mol fraction of the p-phenylene sulfide recurring unitsin the resulting block copolymer will be 0.50 to 0.98). If necessary,the water content of the mixture is controlled again, and the mixture isheated to a suitable temperature, preferably 160° to 300° C.,particularly 200° to 280° C. to carry out the polymerization reaction.In this manner, the crystalline p-phenylene sulfide block copolymer ofthe present invention is obtained. If necessary, the polymer isneutralized, filtered, washed and dried to recover the same in the formof granules or a powder.

The latter step in the production process (I) is carried out for forminga block consisting essentially of units (B). An indispensable matter tobe introduced in this step is a dihaloaromatic compound consistingessentially of a m-dihalobenzene. Therefore, the other startingmaterial, i.e., the alkali metal sulfide, and the organic solvent forthe block formation can be those used in the former step withoutnecessitating fresh ones. In this case, the amount(s) of the alkalimetal sulfide and/or organic solvent introduced in the former stepis(are) increased, if necessary. As a matter of course, this mode ispossible also in the following production process (II).

Production process (II)

The production process (II) is different from the process (I) in thatthe blocks of the recurring units (B) are formed first. The process IIis preferable to the process (I) because the second step in II can becarried out with more ease than the second step in I sincep-dihalobenzene polymerizes with more ease than m-dihalobenzene.

Particularly for obtaining block copolymers having a high molecularweight, the process (II) is the most effective among the three processesdescribed above.

Generally, the following relationship is recognized: ##EQU3## wherein: nrepresents an average length (degree of polymerization) of the block ofp-phenylene sulfide recurring units (A); X represents a mol fraction;and m represents an average length of the block of recurring unit Bconsisting essentially of m-phenylene sulfide.

Therefore, in a block polymer in which n is 20 to 5,000, and m of therecurring unit (B) is in the range of ##EQU4## with the proviso that mis not less than 2. The production process (II) has been developed onthe basis of this relationship.

In this process, the polar organic solvent and the starting alkali metalsulfide having a controlled water content are charged into a reactor inthe same manner as in process (I), the m-dihalobenzene (which cancontain a small amount of a dihalo-substituted aromatic compound) isadded thereto in such an amount that the molar ratio thereof to thesulfide will be 0.95/1 to 1.05/1, and the mixture is heated to asuitable temperature, particularly 160° to 300° C., preferably 190° to260° C., to carry out the polymerization reaction until the averagedegree of polymerization of the resulting arylene sulfide prepolymerreaches ##EQU5## Thus, a reaction liquid mixture (E) containing theprepolymer is obtained.

On the other hand, the polar organic solvent and the starting alkalimetal sulfide having a controlled water content are charged into areactor in the same manner as in the process (I). A p-dihalobenzene isadded thereto in such an amount that the molar ratio thereof to thesulfide will be 0.95/1 to 1.05/1 to obtain an unreacted liquid mixture(F). As described above, the essentially indispensable component of themixture (F) is the p-dihalobenzene, and this mixture can be free of thesulfide and solvent.

The unreacted liquid mixture (F) is mixed with the prepolymer-containingreaction mixture (E) obtained as above in a specific ratio. Ifnecessary, the water content of the resulting mixture is controlledagain, and the mixture is heated to a suitable temperature, particularly160° to 300° C., preferably 200° to 280° C., to carry out thepolymerization reaction. Thus, the crystalline p-phenylene sulfide blockcopolymer of the present invention is obtained. The polymer may berecovered and purified in the same manner as in the process (I).

Production process (III)

In this process, the blocks are formed separately and are then combinedtogether.

The liquid reaction mixture (C) obtained in the process (I) is mixedwith the liquid reaction mixture (E) obtained in the process (II) in agiven ratio. If necessary, the water content of the resulting mixture iscontrolled, and then the mixture is heated to a suitable temperature,particularly 160° to 300° C., preferably 200° to 280° C., to cary outthe polymerization reaction. Thus, the crystalline p-phenylene sulfideblock copolymer of the present invention is obtained. The polymer may berecovered and purified in the same manner as in the process (I).

Uses of the Block Copolymer

The block copolymer of the present invention is usable for theproduction of various molded articles preferably in the form of at leasta monoaxially stretch-oriented product.

Films

The crystalline p-phenylene sulfide block copolymer of the presentinvention can be shaped into films or sheets by an inflation method orT-die method. The films or sheets obtained by the T-die method can befurther stretched into oriented films by means of a tenter, etc.

The block copolymer of the present invention can be shaped directly intoa biaxially oriented film by heating the same to a temperature of atleast Tm to melt the same and then expanding it to a 5 to 500 times asarea ratio at a resin temperature in the range of Tc₂ to 350° C. Thestretch-oriented film can further be converted to a heat resistant,stretch-oriented film having an increased degree of crystallization byheat-treating (i.e., heat-setting) the same at a temperature in therange of Tc₁ to Tm while the contraction or elongation is limited to upto 20% or while the size is kept unchanged.

In the T-die film formation method, the block copolymer of the presentinvention is melted by heating it to a temperature of at least Tm, andthe melt is extruded through a T-die while the resin temperature is heldabove Tc₂ and below 350° C., the extrusion product being cooled rapidlyor gradually and wound to obtain a non-oriented sheet or film. Thissheet or film can be stretched monoaxially or biaxially to 2 to 20 timesthe initial area by means of a tenter or the like at a temperature inthe range of Tg to Tc₁.

These non-oriented sheets or films or stretch-oriented films can also beconverted into a heat-resistant film having an increased degree ofcrystallization by heat-setting the same at a temperature in the rangeof Tc₁ to Tm while the contraction or elongation is limited to up to 20%or while the size is kept unchanged.

The films or sheets thus obtained from the crystalline p-phenylenesulfide block copolymer of the present invention have a Tm of 250° to285° C., Tg of 20° to 80° C., Ci of 15 to 85, and thickness of 1 μm to 5mm. The films heat set after the stretch orientation has a Ci of 40 to85 and thickness of 1 μm to 2 mm.

Filaments

Stretched filaments can be produced from the crystalline p-phenylenesulfide block copolymer of the present invention by heating it to atemperature of Tm to 400° C., extruding the obtained melt through anozzle, spinning the same at a resin temperature of Tc₂ to 350° C., andstretching the extrusion product to 2 to 20-folds at a temperature inthe range of Tc₁ to Tm.

When the stretched filament is blended with carbon fibers, glass fibersor aramide fibers and the obtained blend is heated to a temperaturehigher than its melting point, a stampable sheet can be obtained. Thestretched filament can be converted into a heat-resistant one having anincreased degree of crystallization (Ci: 40 to 90) by heat-setting thesame at a temperature in the range of Tc₁ to Tm while the contraction orelongation is limited to up to 20%, or while the size is kept unchanged.

Electric wire coating

Electric wires can be coated with the crystalline p-phenylene sulfideblock copolymer of the present invention or a composition comprisingthis copolymer and an inorganic filler by heating the copolymer or thecomposition to a temperature in the range of Tm to 400° C. to melt thesame and then coating the wire with the melt extruded through acrosshead die. When the stretch ratio in the first stretching iscontrolled to 50 to 500-folds and the temperature in the subsequent heattreatment is controlled in the range of Tc₁ to Tm to accomplish the heatsetting, a tough, heat-resistant coated electric wire having a Ci of 15to 70 can be obtained.

Extrusion-molded products

Tough, heat-resistant extrusion molded articles such as plates, pipes,rods and profiles having a Ci of 15 to 60 can be obtained from thecrystalline p-phenylene sulfide block copolymer of the present inventionor from a composition comprising the copolymer and a fibrous or powderyfiller by heating the same to a temperature in the range of Tm to 400°C., extruding the obtained melt through a molding die, cooling theextrusion product rapidly or gradually and heat-treating the product ata temperature of Tc₁ to Tm.

Injection-molded products

Tough, heat-resistant moldings can be obtained from the crystallinep-phenylene sulfide block copolymer of the present invention or from acomposition comprising the copolymer and a fibrous or powdery filler byheating the same to a temperature in the range of Tm to 400° C.,injecting the obtained melt into a mold and heat setting the product ata temperature in the range of Tc₁ to Tm. The block copolymer of thepresent invention is suitable particularly for the production of largemolded articles and thick molded structures, since rough spheruliteswhich cause cracks are not easily formed.

Compositions

The crystalline p-phenylene sulfide block copolymer of the presentinvention can also be melt-mixed with a powdery inorganic filler such asmica, TiO₂, SiO₂, Al₂ O₃, CaCO₃, carbon black, talc, CaSiO₃ or MgCO₃ orwith a fibrous filler such as glass, carbon, graphite or aramide fiberto form a composition. This copolymer can be blended also with, forexample, a poly-p-phenylene sulfide, poly-m-phenylene sulfide,polyphenylene sulfide random copolymer, polyimide, polyamide, polyetherether ketone, polysulfone, polyether sulfone, polyetherimide,polyarylene, polyphenylene ether, polycarbonate, polyethyleneterephthalate, polybutylene terephthalate, polyacetal, polypropylene,polyethylene, ABS, polyvinyl chloride, polymethyl methacrylate,polystyrene, polyvinylidene fluoride, polytetrafluoroethylene ortetrafluoroethylene copolymer to form a composition.

The crystalline p-phenylene sulfide block copolymer of the presentinvention can be converted into a high molecular ion complex by reactingthe same with an alkali metal or alkaline earth metal hydroxide, oxideor alkoxide (including phenoxide) at a temperature of 200° to 400° C.(reference: specification of Japanese Patent Application No.95705/1984).

Secondary uses

The heat-resistant films and sheets obtained from the crystallinep-phenylene sulfide block copolymer of the present invention or acomposition thereof are useful as starting materials for printed circuitboards, magnetic tapes (both coated type and vapor-deposited type),insulating tapes and floppy discs in the electronic and electrictechnical fields. The extrusion-molded products (such as plates, pipesand profiles) are useful as printed circuit boards and protective tubesfor wire assemblies in the electronic and electric art and asanti-corrosive, heat-resistant pipes and tubes in the technical field ofchemical industry. Electric wires coated with these materials are usefulas heat-resistant, anticorrosive electric wires. The injection-moldedproducts are useful as IC-sealing materials, printed circuit boards,connectors and parts for microwave machineries in the electronic andelectric field and as large-sized pumps, large-sized valves, sealingmaterials and lining materials in the chemical industry.

Printed Circuit Boards

One of the secondary uses of these films and sheets is the use of theabove-mentioned block copolymer as a resin component for printed circuitboards.

Printed circuit boards according to the present invention are as definedabove.

Block copolymer

The mol fraction of the recurring units ##STR26## blocks in themolecular chain is in the range of 0.50 to 0.98, preferably 0.60 to0.90. By controlling the mol fraction within this range, thecrystallinity can be maintained while the excellent adhesion between thebase and the metal is retained.

The block copolymer of the present invention has a melt viscosity (η*)of 300 to 50,000 P, particularly preferably 300 to 30,000 P, asdetermined at 310° C. at a shear rate of 200 sec⁻¹. When the copolymerhas a melt viscosity of less than 300 P (i.e., a low molecular weight),its strength is insufficient for the production of the printed circuitboards. When the melt viscosity exceeds 50,000 P, molding becomesdifficult. The block copolymer of the present invention has acrystalline melting point (Tm) preferably in the range of 200° to 350°C. When the crystalline melting point is less than 200° C., the heatresistance is insufficient for printed circuit boards, and when itexceeds 350° C., molding operation becomes difficult.

The number of the recurring units ##STR27## i.e., the degree ofpolymerization of the polyphenylene sulfide block component, isdetermined according to a fluorescent X-ray method. The mol fraction canbe determined easily according to infrared analysis. The crystallizationtemperature is a value represented by a melting peak as determined byusing 10 mg of the sample at a rate of 10° C./min. by means of adifferential scanning calorimeter.

The base resin for the printed circuit boards according to the presentinvention is a polymer comprising mainly the phenylene sulfide blockcopolymer. The term "comprising mainly" herein indicates that the amountof the phenylene sulfide block copolymer is predominant.

Fibrous reinforcing materials

The fibrous reinforcing materials used in the present invention includessynthetic inorganic fibers (such as glass fibers, silica fibers, aluminafibers and ceramic fibers), excluding electroconductive ones such asmetals and carbonaceous fibers; natural inorganic fibers (such as rockwool); synthetic organic fibers (such as aromatic amide fibers, phenolfibers and cellulose fibers); and natural organic fibers (such as pulpsand cotton). From the viewpoints of electrical insulation properties,heat resistance, strength and economy, synthetic inorganic fibers,particularly glass fibers, are preferred.

The fibrous reinforcing materials may be in the form of any of shortfibers, long fibers, papers, mats, felts and knits as long as they havean aspect ratio (fiber length/fiber diameter) of at least 10. In theproduction of the printed circuit boards by the injection moldingmethod, short fibers are particularly preferred, in general. When theextrusion molding or compression molding method is employed, the form ofthe fibers is not limited. When the inorganic fibers are used as fibrousreinforcing material and an improvement of the wettability thereof withthe phenylene sulfide block copolymer (base resin) is desired, treatmentof the surface with a silane coupling agent (such as epoxysilane ormercaptosilane) is effective. It is also possible to use commerciallyavailable, surface-treated inorganic fibers.

The amount of the fibrous reinforcing material is determined suitably sothat the amounts of the phenylene sulfide block copolymer and thefibrous reinforcing material will be 50-95 vol. % and 5-50 vol. %,respectively, based on the total volume thereof (their volumes can beeasily determined by actual measurement or calculation based on therelationship between weight and specific gravity). When the amount ofthe fibrous reinforcing material is less than the above indicated value,adequate effect thereof cannot be obtained. On the other hand, when itexceeds the indicated upper limit, the properties of the phenylenesulfide block copolymer cannot be exhibited satisfactorily.

The phenylene sulfide block copolymer used as the base resin accordingto the present invention may contain, in addition to the fibrousreinforcing material, a small amount of a filler (such as calciumcarbonate, titanium oxide, silica or alumina), anti-oxidant, stabilizer,lubricant, crystallization nucleating agent, colorant, releasing agentand other resins provided their effects are not counter to the objectsof the invention.

Metal Layer

For the metal layer to be formed on the printed circuit board of thepresent invention, a thin layer of copper, aluminum, silver, gold layeror the like can be used. Of these, a copper or aluminum layer isrepresentative.

Preparation of Printed Circuit Board Molding of Base Material

The process for molding the composite of the phenylene sulfide blockcopolymer and the fibrous reinforcing material of the present inventioninto the plates is not particularly limited.

In the injection molding process, the plates can be molded by injectinga blend of the phenylene sulfide block copolymer, and the fibrousreinforcing material into a mold by means of an injection moldingmachine. When a specially designed mold is used, moldings having throughholes can be prepared directly. This process is advantageous in that asubsequent hole-forming step is unnecessary. When a metal foil having apunched pattern is inserted, the printed-circuit board can be obtaineddirectly. By this process the number of steps in the production of theprinted circuit board can be reduced remarkably.

In one mode of production of a plate by extrusion molding process, ablend or laminate comprising the fibrous reinforcing material and thephenylene sulfide block copolymer is introduced between a pair of metalbelts to carry out continuous compression, heating, and melting. If ametal foil is placed on one or both surfaces thereof, plate having ametal layer can be obtained directly.

In one mode of production of a plate by the compression molding process,a blend or laminate comprising the phenylene sulfide block copolymer andthe fibrous reinforcing material is charged into a mold and subjected tocompression, heating and melting to obtain the plate. If a metal foil isplaced on one or both surfaces thereof, a plate having metal layer(s)can be obtained directly also in this case.

Production of printed circuit boards

In the production of printed circuit boards by forming a metal layer ofa circuit pattern on an insulating board obtained by molding a compositeof the phenylene sulfide block copolymer of the present invention andthe fibrous reinforcing material, the production process is notparticularly limited.

For example, a so-called subtractive method which comprises bonding ametal foil to a board (this operation may be omitted when the metal foilis applied in the course of the preparation of the board), and removingunnecessary parts of the metal foil by etching to form a circuit patterncan be used. When a board having no metal foil layer, particularly aboard obtained by the injection molding method, is used, a so-calledadditive method wherein a circuit pattern is formed by a metal platingin necessary parts on the board or a so-called stamping foil methodwherein a metal foil having a previously stamped pattern is appliedthereto can be adopted.

The bonding of the metal foil to the board comprising a composite of thephenylene sulfide block copolymer of the present invention and thefibrous reinforcing material can also be accomplished by means of anadhesive (such as nitrile rubber, epoxy or urethane adhesive) after theproduction of the board by molding. In another process, the metal foilis bonded to the board by melt-contact-bonding in the course of themolding of the board or after the molding without using any adhesive.

Further, the circuit pattern can also be formed directly by metalplating. When a plating process is employed, the surface of the board ispretreated by a physical or chemical method such as mechanical abrasionor treatment with an organic solvent (such as a carboxylic acid amide,ether, ketone, ester, aromatic hydrocarbon, halogenated hydrocarbon,urea derivative or sulfolane), an oxidizing agent (such as chromic acid,permanganic acid or nitric acid), or a solution of a Lewis acid (such asAlCl₃, TiB₄, SbF₅, SnCl₄ or BF₃) so as to make the surface rough. Bythis treatment, the adhesion between the metal layer and the insulatingboard can be increased. This effect is further improved by incorporatinga fine powder of calcium carbonate or titanium oxide in the startingmaterials for the board. The adhesion between the metal and the boardcomprising the phenylene sulfide copolymer base resin of the presentinvention can be improved by this pretreatment since the surface of theboard is roughened suitably because of the characteristic properties ofthe block copolymer, while such an adhesion-improving effect cannot beobtained by the same pretreatment in a board comprising an ordinarypoly-p-phenylene sulfide base resin. This is one of the importantcharacteristic features of the insulating base.

Sealing or Encapsulation Compositions

Another secondary use of the block copolymer is the use thereof as asealing or encapsulation composition comprising this block copolymer asa resin component.

The sealing composition of the present invention and the sealing processwith the use thereof are as follows.

Block copolymers

The presence of the blocks comprising ##STR28## assures thecrystallinity of the copolymer and heat resistance thereof owing to thecrystallinity. The presence of the recurring units ##STR29## causes (1)a lowering of the melt viscosity of the copolymer to remarkably improvethe injection moldability thereof, (2) prevention of the formation ofspherulites to prevent crack formation or cutting or deformation ofbonding wires, and (3) improvement of the adhesion to the lead frame orthe bonding wire to greatly improve high-temperature moisture resistanceof particularly the sealed electronic parts. Thus, by the introductionof the recurring units ##STR30## the defects of the p-phenylene sulfidehomopolymer can be overcome.

The average degree of polymerization of the ##STR31## blocks in theblock copolymer of the present invention is in the range of 20 to 2,000,preferably 40 to 1,000. With an average degree of polymerization lessthan 20, the crystallinity of the polymer is insufficient, and themolded articles obtained therefrom would have insufficient heatresistance. When the average degree of polymerization exceeds 2,000, themolecular weight of the copolymer is excessive, and properties thereofare like those of the p-phenylene sulfide homopolymer. As a result,molded articles having cracks, broken bonding wire, or poorhigh-temperature moisture resistance are unfavorably formed.

The melt viscosity, which is an index of the molecular weight, of thephenylene sulfide block copolymer of the present invention is suitablyin the range of 10 to 1,500 P (at 310° C. and a shear rate of 200sec⁻¹), particularly 50 to 800 P. When the melt viscosity is less than10 P, the molecular weight is too low to obtain molded articles of ahigh strength. When it is as high as higher than 1,500 P, bonding wireis broken in the injection molding step or an insufficient filling isunfavorably caused.

The sealing composition of the present invention may contain, inaddition to the phenylene sulfide block copolymer (main resincomponent), a small amount of other thermoplastic resins (such aspoly-m-phenylene sulfide, poly-p-phenylene sulfide, m-phenylenesulfide/p-phenylene sulfide random copolymer, polybutyreneterephthalate, polyethylene terephthalate, polyether sulfone andpolyamide) and thermosetting resins (such as epoxy resin, silicone resinand urethane resin) provided that the characteristic features of thecomposition are not impaired. The amount of the main resin component,i.e., phenylene sulfide block copolymer, is at least 60 wt. % based onthe total resin. A preferred minor resin component is poly-m-phenylenesulfide or poly-p-phenylene sulfide.

Fillers

The inorganic fillers which can be contained in the sealing compositionof the present invention include fibrous fillers, non-fibrous fillers,and combinations thereof.

Examples of non-fibrous fillers are quartz powder, glass powder, glassbeads, alumina powder, TiO₂ powder, iron oxide powder, talc, clay andmica. The particle size of these fillers is preferably up to 0.5 mmsince larger particles unfavorably cause the breaking of bonding wires.

Examples of fibrous fillers are glass fibers, silica fibers,wollastonite, potassium titanate fibers, processed mineral fibers andceramic fibers. Those having a fiber length of up to 0.5 mm and anaspect ratio of at least 5 are preferred. Fibers longer than 0.5 mmcause breakage of bonding wire, and those having an aspect ratio of lessthan 5 unfavorably have insufficient reinforcing effect.

When an inorganic filler is mixed into the sealing composition of thepresent invention, the amount thereof is preferably 20 to 300 wt.%,particularly 50 to 200 wt.%. With more than 300 wt.%, the melt viscosityof the composition becomes excessive, and breakage of bonding wire iscaused. A content less than 20% of the inorganic filler is undesirablebecause the thermal expansion coefficient becomes high to cause breakageof bonding wire.

In the case where an inorganic filler is mixed into the sealingcomposition of the present invention, the inorganic filler can be madehydrophobic by treating the same with a surface-treating agent such as asilane coupling agent or titanate coupling agent so as to improve theadhesion of the filler with the resin or to reduce its hygroscopicity.Alternatively, these treating agents can also be mixed into the sealingcomposition. Further, a water-repellent such as a modified silicone oil,fluorine oil or paraffin can be mixed into the sealing composition so asto increase the moistureproofness of the composition. Further,assistants such as a lubricant, colorant, releasing agent, heatstabilizer and curing agent may be added into the sealing composition ofthe present invention provided that they are not counter to the objectsof the invention.

Sealing or Encapsulation of Electronic Parts

After mixing the synthetic resin component, inorganic filler and, ifnecessary, other additives, the resulting composition is used forsealing electronic parts.

The sealing may be conducted by a known process such as injectionmolding or transfer molding process. The molding is conducted with anordinary injection-molding machine or transfer-molding machine under theconditions of a molding pressure of 10 to 200 kg/cm², cylindertemperature of 280° to 370° C. and mold temperature of 80° to 220° C.

A characteristic feature of the present invention, which is that theresin component is a block copolymer having improved crystallinity, canbe exhibited most effectively when the sealing is carried out byinjection molding of the resin composition.

EXPERIMENTAL EXAMPLES Copolymers and Production Thereof SynthesisExample A-1

11.0 kg of NMP (N-methylpyrrolidone) and 20.0 mol of Na₂ S.5H₂ O wereplaced in a 20-liter polymerization pressure vessel. The mixture washeated to about 200° C. to distill off water. (The loss of S due to thedischarge in the form of H₂ S was 1.4 molar % based on charged Na₂ S,and the amount of water remaining in the vessel was 27 mol.) Then 20.1mol of p-DCB (p-dichlorobenzene) and 3.1 kg of NMP were added thereto.After replacement of air with N₂, polymerization reaction was carriedout at 210° C. for 4 hours. 53 mol of water was added to the mixture,and the reaction was continued at 250° C. for 0.5 hour to obtain areaction liquid mixture (C-1), which was taken out and stored. A smallamount of the mixture (C-1) was sampled to determine the degree ofpolymerization of the resulting p-phenylene sulfide prepolymer byfluorescent X-ray method. The degree of polymerization was 320.

11.0 kg of NMP and 20.0 mol of Na₂ S.5H₂ O were charged in a 20-literpolymerization pressure vessel. The mixture was heated to about 200° C.to distill off water (loss of S: 1.5 molar %, amount of water remainingin the vessel: 29 mol). Then, 20.1 mol of m-DCB (m-dichlorobenzene) and3.0 kg of NMP were added thereto. The mixture was cooled under stirringto obtain an unreacted liquid mixture (D-1), which was taken out andstored.

The liquid reaction liquid mixture (C-1), unreacted liquid mixture(D-1), and water were placed in a 1-liter polymerization pressure vesselin proportions of 375 g/88 g/4.6 g, 328 g/131.5 g/6.9 g, and 234 g/219g/11.5 g and they were reacted at 250° C. for 20 hours. After completionof the reactions, the respective liquid reaction mixtures were filtered,washed with hot water, and dried under reduced pressure to obtain blockcopolymers (1-1), (1-2), and (1-3).

Each block copolymer thus obtained was melted at a temperature higherthan its melting point by about 30° C. and pressed with a hot press. Theblock copolymer was cooled rapidly with water to obtain a film having athickness of 0.1 to 0.2 mm. The copolymer composition of this sample wasdetermined according to an infrared analysis (FT-IR method). Tg, Tm, Tc₁and Tc₂ of this sample were also measured.

Each film was heat-treated at a temperature lower than its melting pointby 20° C. for 20 min. to obtain a heat-treated, crystallized sheet. Thecrystallization index Ci of the sheet was measured by X-ray diffractionmethod.

The results are summarized in Table A-1.

Synthesis Example A-2

11.0 Kg of NMP and 20.0 mol of Na₂ S.5H₂ O were placed in a 20-literpolymerization pressure vessel. The mixture was heated to about 200° C.to distill off water (loss of S: 1.5 molar %, and amount of waterremaining in the vessel: 28 mol). Then, 20.1 mol of m-DCB and 3.0 kg ofNMP were added thereto. After replacement of air with N₂, thepolymerization reaction was carried out at 210° C. for 8 hours. 52 molof water was added to the mixture and the reaction was continued at 250°C. for 0.5 hour to obtain a reaction liquid mixture (E-2), which wastaken out and stored.

A small amount of the liquid (E-2) was sampled to determine the degreeof polymerization of the resulting m-phenylene sulfide prepolymer by theGPC method. The degree of polymerization was 60.

11.0 kg of NMP and 20.0 mol of Na₂ S.5H₂ O were placed in a 20-literpolymerization pressure vessel. The mixture was heated to about 200° C.to distill off water (loss of S: 15 molar %, amount of water remainingin the vessel: 26 mol). Then, 20.2 mol of p-DCB and 3.0 kg of NMP wereadded thereto. The mixture was cooled under stirring to obtain anunreacted liquid mixture (F-2), which was taken out and stored.

The liquid reaction liquid mixture (E-2), unreacted liquid mixture (F-2)and water were placed in a 1-liter polymerization pressure vessel inproportions of 97 g/350 g/19.4 g, 140.5 g/306 g/17 g and 234 g/218.5g/12.2 g and were reacted at 250° C. for 20 hours. After completion ofthe reactions, the respective liquid reaction mixtures were filtered,washed with hot water and dried under reduced pressure to obtain blockcopolymers (2-1), (2-2) and (2-3).

The mol fractions (X) of the recurring units The mole fraction (X) ofrecurring units ##STR32## in the blocks were determined by infraredanalysis and found to be 0.86, 0.79, and 0.68, respectively. The degreeof polymerization of ##STR33## was calculated from the value of Xaccording to the formula: ##EQU6## The results are shown in Table A-1together with the physical properties.

Synthesis Example A-3

The liquid reaction mixtures (C-1) and (E-2) obtained in SynthesisExamples A-1 and A-2 were placed in the reactor in amounts of 422 g/47g, 375 g/94 g, 328 g/140.5 g and 234 g/234 g and were reacted at 250° C.for 20 hours. After completion of the reactions, the reaction mixtureswere filtered, washed with hot water, and dried under reduced pressureto obtain block copolymers (3-1), (3-2), (3-3), and (3-4).

The physical properties thereof were as shown in Table A-1.

Synthesis Example A-3

A liquid reaction mixture (C-3) containing p-phenylene sulfideprepolymer was produced as in Synthesis Example A-1 except that thepolymerization was carried at 210° C. for 3 hours in a 20-literpolymerization pressure vessel. Further, an unreacted liquid mixture(D-3) containing m-DCB was produced in the same manner as in SynthesisExample A-1 in a 20-liter polymerization pressure vessel.

7,170 g of the liquid (C-3), 1,190 g of the liquid (D-3) and 60 g ofwater were placed in a 10-liter polymerization pressure vessel, andreaction thereof was carried out at 255° C. for 15 hours. Aftercompletion of the reaction, a block polymer was recovered from thereaction liquid in the same manner as in Synthesis Example A-1. Thepolymerization was carried out in the same manner as above in 4 batches.The polymers obtained in total of 5 batches were blended togetherhomogeneously and then shaped into polymer pellets (3-1) with apelletizer. The p-phenylene sulfide prepolymer had an average degree ofpolymerization of 260.

A liquid reaction mixture (E-3) containing m-phenylene sulfideprepolymer was obtained as in Synthesis Example 2 except that thepolymerization reaction was carried out at 210° C. for 6 hours in a20-liter polymerization pressure vessel. An unreacted liquid mixture(F-3) containing p-DCB was obtained in the same manner as in SynthesisExample A-2 in a 20-liter polymerization pressure vessel.

7,170 g of the liquid (F-3), 1190 g of the liquid (E-3) and 60 g ofwater were placed in a 10-liter polymerization pressure vessel, andreaction was carried out at 255° C. for 15 hours. After completion ofthe reaction, a block copolymer was recovered from the reaction liquidin the same manner as in Synthesis Example A-1. The polymerization wasrepeated in 5 batches in the same manner as above. The polymers obtainedin the total of 6 batches were blended together homogeneously and thenshaped into polymer pellets (3-2) with a pelletizer. The m-phenylenesulfide prepolymer had an average degree of polymerization of 50.

Comparative Synthesis Example A-1

500 g of NMP and 1.00 mol of Na₂ S.3H₂ O were placed in a 1-literpolymerization pressure vessel. The mixture was heated to about 200° C.to distill off water (loss of S: 1.6 molar %, amount of water remainingin the vessel: 1.4 mol). Then, 0.867 mol of p-DCB, 0.153 mol of m-DCBand 150 g of NMP were added thereto. After replacement of air with N₂,polymerization reaction was carried out at 210° C. for 5 hours. 2.6 molof water was added, and the polymerization reaction was continued at250° C. for 20 hours. After completion of the reaction, a randomcopolymer (comp. 1) was recovered from the reaction liquid in the samemanner as in Synthesis Example 1. The properties of the resulting randomcopolymer were examined in the same manner as in Synthesis Example A-1to obtain the results shown in Table A-1.

Comparative Synthesis Example A-2

625 g of NMP and 1.00 mol of Na₂ S.3H₂ O were placed in a 1-literpolymerization pressure vessel. The mixture was heated to about 200° C.to distill off water (loss of S: 1.5 molar %, amount of water remainingin the vessel: 1.4 mol). Then, 1.01 mol of p-DCB and 155 g of NMP wereadded thereto. After replacement of air with N₂, polymerization reactionwas carried out at 200° C. for 2.5 hours. After completion of thereaction, the resulting liquid reaction liquid mixture (C-Comp. 1) wastaken out and stored. The resulting p-phenylene sulfide prepolymer had adegree of polymerization of up to 5.

400 g of the reaction liquid mixture (C-Comp. 1), 66 g of the unreactedliquid mixture (D-1) obtained in Synthesis Example A-1 and 3.5 g ofwater were placed in a 1-liter polymerization pressure vessel. Thereaction was further carried out at 250° C. for 20 hours. Aftercompletion of the reaction, a block polymer (Comp. 2) was recovered fromthe reaction liquid in the same manner as in Synthesis Example A-1. Theproperties of this product were examined in the same manner as above toobtain the results shown in Table A-1.

Comparative Synthesis Example A-3

11.0 kg of NMP and 20.0 mol of Na₂ S.5H₂ O were placed in a 20-literpolymerization pressure vessel. The mixture was heated to about 200° C.to distill off water (loss of S: 1.4 molar %, amount of water remainingin the vessel: 28 mol). Then, 20.1 mol of p-DCB and 3.1 kg of NMP wereadded thereto. After replacement of air with N₂, polymerization reactionwas carried out at 210° C. for 5 hours. 52 mol of water was addedthereto, and the polymerization reaction was continued at 250° C. for 10hours. After completion of the reaction, a p-phenylene sulfidehomopolymer was recovered from the reaction liquid in the same manner asin Synthesis Example A-1. The polymerization was carried out in the samemanner as above in 3 batches. The polymers obtained in the total of 4batches were blended together and then shaped into polymer pellets(Comp. 3) with a pelletizer. The properties of the thus obtainedhomopolymer were examined in the same manner as in Synthesis Example A-1to obtain the results shown in Table A-1.

Synthesis Example A-5

Except that the post polymerization temperature was 260° C. and theduration was 12 hrs, preparation of a block copolymer was carried out inthe same manner with the case of preparing polymer (1-1), and a blockcopolymer (5-1) was obtained. Except that post polymerizationtemperature was 260° C. and the duration was 8 hrs, preparation of ablock copolymer was made in the same manner with the case of preparingpolymer (2-1), and a block copolymer (5-2) was obtained. Except thatpost polymerization temperature was 260° C. and the duration was 8 hrs,preparation of a block copolymer was made in the same manner with thecase of preparing polymer (3-2), and a block copolymer (5-3) wasobtained. The recurring unit ratio ##STR34## of the block copolymers of(5-1), (5-2) and (5-3) was 83/17, 84/16 and 82/18 (basic mole/basicmole), respectively, and the melt viscosity was 2100, 3500 and 100 P,respectively. Among these block copolymer, polymer (5-2) had the highestmelt viscosity, although the total polymerization duration was all thesame in each case (16.5 hrs).

                                      TABLE A1                                    __________________________________________________________________________    Synthesis   Polymer-                                                                           Polymer Composition                                                                         Length of a                                                                         Physical Properties of Heat-Treated      Example                                                                              Polymer                                                                            ization                                                                            recurring                                                                             basic molar                                                                         block of                                                                            Pressed Film                             No.    code process                                                                            unit    % ratio                                                                             unit A                                                                              η*                                                                           Tg                                                                              Tm Tc.sub.1                                                                          Tc.sub.2                                                                          Ci  Remarks              __________________________________________________________________________    Example A-1                                                                          1-1  (I)  *.sup.2 PP/MP*.sup.3                                                                  = 84/16                                                                             320   1500                                                                             76                                                                              280                                                                              135 193 33  crystalline          "      1-2  "    PP/MP   = 77/23                                                                             320   1700                                                                             72                                                                              275                                                                              145 175 36  "                    "      1-3  "    PP/MP   = 63/37                                                                             320    600                                                                             59                                                                              265                                                                              143 166 29  "                    Example A-2                                                                          2-1  (II) PP/MP   = 86/14                                                                             370*.sup.1                                                                          2200                                                                             75                                                                              275                                                                              140 190 35  "                    "      2-2  "    PP/MP   = 79/21                                                                             225*.sup.1                                                                          2000                                                                             74                                                                              275                                                                              140 180 30  "                    "      2-3  "    PP/MP   = 68/32                                                                             130*.sup.1                                                                           700                                                                             62                                                                              260                                                                              148 170 27  "                    Example A-3                                                                          3-1  (III)                                                                              PP/MP   = 81/19                                                                             320   2100                                                                             78                                                                              281                                                                              134 203 34  "                    "      3-2  "    PP/MP   = 82/18                                                                             320   2300                                                                             76                                                                              280                                                                              137 196 35  "                    "      3-3  "    PP/MP   = 75/25                                                                             320   2500                                                                             72                                                                              273                                                                              145 173 30  "                    "      3-4  "    PP/MP   = 61/39                                                                             320    800                                                                             61                                                                              260                                                                              135 165 26  "                    Example A-3                                                                          3-1  (I)  PP/MP   = 88/12                                                                             260   1000                                                                             77                                                                              281                                                                              125 205 37  "                    "      3-2  (II) PP/MP   = 87/13                                                                             340*.sup.1                                                                          2500                                                                             73                                                                              275                                                                              139 200 32  "                    Comparative                                                                          Comp. 1                                                                            --   PP/MP   = 86/14                                                                             --     300                                                                             --                                                                              -- --  --   0  amorphous            Example A-1                                                                   Comparative                                                                          Comp. 2                                                                            (I)  PP/MP   = 88/12                                                                             <5    1500                                                                             --                                                                              -- --  --  ≈0                                                                        "                    Example A-2                                                                   Comparative                                                                          Comp. 3                                                                            --   PP/MP   = 100/0                                                                             --    6200                                                                             90                                                                              285                                                                              131 237 38  crystalline          Example A-3                                                                   __________________________________________________________________________     *.sup.1 value calculated from the formula: n = m X/(1 - X)                    ##STR35##                                                                     ##STR36##                                                                

Molding Example A-1

The polymer pellets (3-1), (3-2) and (Comp. 3) obtained in SynthesisExample A-3 and Synthesis Comparative Example A-3 were melted by heatingto a temperature above their melting points in a 35 mm φ extruderprovided with a circle die (diameter of opening: 30 mm, clearance: 1mm). The molten resins were supercooled to 220° to 250° C. in the dieand airing part and expanded by stretching 6-8-folds in the machinedirections to form inflated films. The average thicknesses of thebiaxially oriented films obtained from the polymer pellets (3-1), (3-2),and (Comp. 3) were 20, 20, and 45 μm, respectively.

The inflated films were heat-treated at 260° C. for 10 minutes while thesizes thereof were kept constant. The films obtained from the polymers(4-1) and (4-2) could be heat-set uniformly and were biaxially orientedfilms having a high transparency, high degree of crystallization andsmooth surface. On the other hand, the film obtained from the polymer(Comp. 3) was opaque and had a wavy surface, since whitening andwrinkling were caused in the course of the heat treatment. Thisphenomenon of the polymer (Comp. 3) was considered to be due to a rapidcrystallization which occurred in the inflation step, and whichinhibited ample expansion and orientation. The heat set films obtainedfrom the polymers (3-1) and (3-2) had crystallization indexes of 68 and65, respectively.

A part of the pellets obtained from each of the polymers (3-1), (3-2)and (Comp. 3) was hot-pressed at 310° C. and rapidly cooled to form anamorphous film having a thickness of about 0.2 mm. It was then stretched3.0×3.0 fold by a biaxial stretching machine of T. M. Long Co. at 87°C., 87° C. and 103° C. to obtain stretched films. This film washeat-treated at 260° C. for 10 minutes to obtain a heat-set film havinga high transparency. These heat-set films had thicknesses of 10, 8, and9 μm, respectively, Ci of 75, 73, and 80, respectively, crystal sizes[determined from the diffraction peaks (2, 0, 0) obtained by the X-raydiffraction method according to a Schelle's formula] of 71, 78, and 75Å, respectively, and coefficients of heat contraction of 12, 17, and13%, respectively.

Molding Example A-2

Non-stretched monofilaments were produced from the pellets of each ofthe polymers (3-1), (3-2) and (Comp. 3) by winding at a rate of 4 m/min.at 320° C. on the average (take-off ratio R₁ =10) through a nozzlehaving a diameter of 1 mm and a length of 5 mm by using a melttensiontester. The non-stretched monofilaments were immersed in an oilbath at 85° C., 85° C., and 95° C. and stretched with a jig to examinetheir stretchabilities. The non-stretched filaments obtained from thepolymers (3-1) and (3-2) had a break rate of less than 10% even afterstretching 8-fold, while those obtained from the polymer (Comp. 3) had abreak rate of higher than 90% after stretching 8-fold probably becausecrystallization had proceeded in the spinning step. The average tensilemoduli of elasticity and average elongations of the fibers which werenot broken by the 8-fold stretching (30 to 90 μm) were 530, 500 and 590(kg/mm²), respectively, and 100, 120 and 60%, respectively.

These fibers were heat-treated at 230° C. for 1 second to accomplishheat setting, while the elongation was limited to 3%. The averagetensile moduli of elasticity and average elongations of the heat-setfilaments were 800, 740, and 960 kg/mm², respectively, and 33, 35, and18%, respectively.

Molding Example A-3

Copper wires having a diameter of 1 mm were melt-coated with pelletsobtained from the polymer (3-1) and (Comp. 3) by means of a small-sizedextruder (19 mmφ provided with an electric wire-coating die tip. Theextruder head temperature was 310° C., and the die tip temperature was270° C. In the melt-coating step, the polymer was stretched to a primarystretching ratio of 140 to 160, immersed in a glycerol bath (140° to160° C.) and then in an infrared heating bath to heat-treat the sameuntil the surface temperature of the coated wires reached about 160° to180° C. Thus, the crystallization was accomplished. Ci were 31 and 41,respectively. The enameled wire-type coated wires thus obtained weresubjected to an adhesion test (9.2 torsion test) and dielectricbreakdown voltage resistance test (11.1.2. single strand method)according to JIS C 3003 (test methods for enameled copper wires andenameled aluminum wires). The results were as follows:

average coating film thickness: 35 and 40 μm

adhesion test: 100-120 times and 80-90 times

dielectric breakdown voltage resistance: >20 (KV/0.1 mm) and ≈15 (KV/0.1mm).

Molding Example A-4

The polymer (3-2) was melted by heating in a 19 mmφ extruder providedwith a die having a ring-shaped opening of a diameter of 10 mm and aclearance of 1 mm. The molten resin was supercooled to 220° to 250° C.in the die and the opening and extruded into the form of a tube, whichwas cooled in a water shower and cut. The obtained tube pieces were heattreated at 130° C. for 1 hour, at 150° C. for 1 hour and at 220° C. for10 hours to bring about crystallization. The heat-treated tubes had a Ciof 28.

Molding Example A-5

The polymer (3-2), glass fiber (length: 2 cm, strands) and mica weremelt-mixed in a 19 mmφ extruder to form pellets containing 50 wt. % ofthe glass fibers and 10 wt.% of mica. The pellets were injection-moldedin an injection-molding machine provided with a mold measuring 1.5 mm×8cm×10 cm at 320° C. to obtain a plate having a thickness of 1.5 mm. Theplate was heat-treated at 250° C. for 4 hours. Ci was 30. Thenon-heat-treated plate thus obtained was interposed between sheets ofcopper foil (of a thickness of 35 μm) which has been surface-treatedwith a zinc/copper alloy. After pressing with a hot press at 320° C. for10 minutes, a copper-coated plate was obtained. This product washeat-treated at 260° C. for 10 minutes. Ci was 26. The peeling strengthof the copper foil was 1.9 kg/cm.

Molding Example A-6

The polymer (3-2) was mixed with 1 wt. % of NaOMe. The mixture wasmelted by heating to 330° C. in a 19-mm diameter extruder and extrudedwhile it was reacted to obtain an ion complex. The product had a meltviscosity of 8,800 P as determined at 310° C. at a shear rate of 200sec⁻¹. It was pressed at 310° C. to obtain a rapidly cooled sheet havinga thickness of about 1.5 mm. This product was interposed between sheetsof copper foil (of a thickness of 35 μm) which had been surface-treatedwith a zinc/copper alloy. After passing with a hot press at 310° C. for5 minutes, a copper-coated plate was obtained. This product washeat-treated at 260° C. for 10 minutes. The peeling strength was 2.1kg/cm.

Printed Circuit Boards Synthesis Example B

(1) 10 kg of N-methylpyrrolidone and 20.0 mol of Na₂ S.5H₂ O were placedin a 20-liter polymerization pressure vessel. The mixture was heated toabout 200° C. to distill off water (loss of S: 1.4 molar %, amount ofwater in the vessel: 30 mol). Then, 20 mol of p-dichlorobenzene and 4 kgof N-methylpyrrolidone were added thereto. Polymerization reaction wascarried out at 210° C. for 5 hours to obtain a reaction liquid mixture(A), which was taken out and stored.

Separately, 10 kg of N-methylpyrrolidone and 20.0 mol of Na₂ S.5H₂ Owere placed in a 20-liter polymerization pressure vessel. The mixturewas heated to about 200° C. to distill off water (loss of S: 1.4 molar%, amount of water present in the vessel: 28 mol). Then, 20.1 mol ofm-dichlorobenzene and 4 kg of N-methylpyrrolidone were added thereto,and the mixture was stirred uniformly to obtain an unreacted liquidmixture (B), which was taken out and stored.

A small amount of the reaction liquid mixture (A) was sampled todetermine the degree of polymerization of the resulting p-phenylenesulfide prepolymer by the fluorescent X-ray method and GPC method. Thedegree of polymerization was 290.

13,280 g of the reaction liquid mixture A, 2,720 g of unreacted liquidmixture B, 8 g of 1,3,5-trichlorobenzene and 800 g of water were chargedin a 20-liter polymerization pressure vessel and were reacted at 250° C.for 19 hours to obtain a polymer. The polymerization was repeated in thesame manner as above in 5 batches. The polymers obtained in the total of6 batches were blended together homogeneously to obtain a polymer A. Thepolymer A had a melt viscosity of 2,600 P as determined at 310° C. at ashear rate of 200 sec⁻¹, degree of polymerization of the ##STR37## blockof 290, mol fraction of ##STR38## units of 0.86, and crystal meltingpoint of 280° C.

(2) Reaction liquid mixture (A) and (B) were prepared in the same manneras above. 12,000 g of the liquid (A), 4,000 g of the liquid (B), 8 g of1,2,4-trichlorobenzene and 400 g of water were charged into a 20-literpolymerization pressure vessel. The reaction was further carried out at255° C. for 15 hours to obtain a polymer. Polymerization was repeated inthe same manner as above in 5 batches. The polymers obtained asdescribed above were blended together homogeneously to obtain a polymerB. The polymer B had a melt viscosity of 2,100 P, degree ofpolymerization of the ##STR39## block of 290, mol fraction of ##STR40##units of 0.79 and crystal melting point of 275° C.

(3) A p-phenylene sulfide homopolymer to be used in a comparativeexample was produced by a process disclosed in the specification ofJapanese Patent Application No. 164,691/1983. In this process, 15 literof N-methylpyrrolidone, 7.0 mol of water and 30 g of p-dichlorobenzenewere charged into a 20-liter pressure autoclave. Then, an anhydrousglass-state ion complex (S²⁻ /Na⁺ /Mg²⁺ /OH⁻ =1/1/2/2) was added theretoin an amount of 30.0 g-equivalent in terms of S²⁻ in the ion complex.After replacement of air with N₂, the mixture was stirred at about 100°C. for 1 hour to obtain a homogeneous dispersion. Then, polymerizationreaction was carried out at 205° C. for 32 hours. The solvent wasremoved, and the polymer was washed in the ordinary manner to obtain ap-phenylene sulfide homopolymer. The polymerization was repeated in thesame manner as above in 5 batches. The polymers thus obtained wereblended together homogeneously to obtain a polymer X. The polymer X hada melt viscosity of 2,300 P and crystal melting point of 286° C.

Example B-1

The polymer A finely divided in a jet pulverizer was applied uniformlyon a glass chopped strand mat (MC 450 A-010 of Nittobo Co., Japan;untreated). The mat was formed into a laminate comprising 4 mat layers.A copper foil (thickness: 35μ) the surface of which had been treatedwith a zinc/copper alloy was placed thereon. The laminate was passedbetween endless metal belts and heated to 320° to 330° C. under pressurein a heating zone. Then the thus treated laminate was cooled and takenoff at about 120° to obtain a plate having a thickness of 1.6 mm and aglass fiber content of 45 vol.%. A part of the product was cut off andtreated by an ordinary subtractive method to obtain a printed circuitboard (1A).

Example B-2

The polymer A or X finely divided in a jet pulverizer was blended with asilane-treated glass chop strand having a fiber length of 6 mm (CS 6PE-401; a product of Nittobo Co., Ltd.) and titanium oxide powder havinga particle diameter of 0.4 μm (Tipaque R-820; a product of IsiharaSangyo Co., Ltd., Japan) in such amounts that a glass content of 30 vol.% would be obtained. The blend was fed into a flat plate mold, pressedat 325° C. under 2 kg/cm² and cooled rapidly to obtain a plate having athickness of about 1.6 mm. A copper foil surface-treated with azinc/copper alloy was applied to the top and bottom inner surfaces ofthe mold, and the plate was interposed between the sheets of a foil andwas pressed at 325° C. under 8 kg/cm² and then at 180° C. under 40kg/cm² to obtain a copper-coated plate. A part of the product was cutoff and treated by an ordinary substractive method to obtain a printedcircuit board plate 2A or 2X.

Example B-3

Three sheets of glass roving cloth cut into the same size (WR 570 C-100of Nittobo Co., Ltd., Japan; treated with a silane) were fed into a flatplate mold. A mixture of the polymer B with the polymer X in a ratio of3:1 was finely pulverized in a jet pulverizer and placed uniformlybetween the sheets and between the sheets of the mold. The laminate waspressed at 325° C. under 4 kg/cm² and cooled with water to obtain aplate having a thickness of 1.6 mm and a glass fiber content of 42 vol.%. Two sheets of a copper foil (35μ) which has been surface-treated witha zinc/copper alloy punched in a circuit pattern were applied to the topand bottom inner surfaces of the mold, and the plate obtained asdescribed above was interposed between the foils. After stamping at 320°C. under 8 kg/cm² followed by pressing at 180° C. under 40 kg/cm² for 30minutes, a printed circuit board 3BX was obtained.

Example B-4

Each of the polymer B and X, finely pulverized with a jet pulverizer wasblended with glass chop strands having a length of 6 mm (CS 6 PE-401; aproduct of Nittobo Co., Ltd., Japan) and calcium carbonate having aparticle diameter of 0.5μ (Super Flex of Pfizer Kyzley Co., Ltd.) in amixer in such amounts that a glass content of 40 vol. % and a claciumcarbonate content of 2 vol. % would be obtained. The mixture was shapedinto pellets with a pelletizer, and the pellets were fed into aninjection-molding machine. After the injection molding at a moldtemperature of 180° C. and a cylinder temperature of 330° C., a platehaving a size of 1.6 mm×100 mm×100 mm was obtained. An adhesive solution[i.e., a solution of 20% of NBR (Nipol #1041; a product of Nippon ZeonCo., Ltd., 4% of phenolic resin (Vercam TD #2645) of Dai-Nippon InkKagaku Co., Ltd.) and 16% of an epoxy resin (Epikote #1001 of ShellChemical Co., Ltd.) in methyl ethyl ketone] was applied to a copper foil(35μ) which has been surface-treated with a zinc/copper alloy andpunched in a circuit pattern. The thus treated copper foil was pressedonto the plates of the polymer B and X at 120° C. After curing at 170°C. for 1 hour, printed circuit boards 4B-1 and 4X-1 were obtained.

Separately, the plates of the polymer B and X were surface-treated witha W solution.sup.(*1) at 80° C. for 30 minutes, then X aqueoussolution.sup.(*2) at room temperature for 3 minutes, Y aqueoussolution.sup.(*3) at room temperature for 5 minutes and Z aqueoussolution.sup.(*4) at 70° C. for 90 minutes to accomplish chemical copperplating. Thus, copper-plated boards 4B-2 and 4X-2 having a copper layerthickness of 9μ on the average were obtained.

(1*) W solution: 5% solution of AlCl₃ in toluene.

(2*) X aqueous solution: 30 g/liter of SnCl₂.2H₂ O and 15 ml/liter ofHCl.

(3*) Y aqueous solution: 0.4 g/liter of PdCl₂, 15 g/liter of SnCl₂ and180 ml/liter of HCl.

(4*) Z aqueous solution: 0.03 m/liter of CuSO₄, 0.23M/liter of NaOH,0.10M/liter of HCHO, 0.04M/liter of EDTA and 50 mg/liter of2,9-dimethyl-1,10-phenanthroline.

A copper foil (suface-treated with a zinc/copper alloy) punched in acircuit pattern was placed in the mold, and then each of the blends ofthe polymers B and X was injected to carry out molding. Thus, printedcircuit boards 4B-3 and 4X-3 were obtained.

The printed circuit boards thus obtained were subjected to a solderingheat resistance test (in which the sample was immersed in a solder bathat 260° C. for 30 minutes, and the appearance thereof was examined) anda metal foil-peeling test (JIS C 6481).

The results are shown in Table B-1.

                  TABLE B1                                                        ______________________________________                                        Printed Volume   Soldering  Peeling                                           Circuit % of     Heat       Strength                                          Board No.                                                                             Fiber    Resistance (kg/cm)                                                                              Remarks                                    ______________________________________                                        1A      45       normal     2.0                                               2A      30       "          1.9                                               2X      30       "          1.0    Comp. Example                              3BX     42       "          1.8                                               4B-1    40       "          1.9                                               4X-1    40       "          0.9    Comp. Example                              4B-2    40       "          1.6                                               4X-2    40       "          0.2    Comp. Example                              4B-3    40       "          2.0                                               4X-3    40       "          1.2    Comp. Example                              ______________________________________                                    

Sealing Agents Synthesis Example C

(1) 11.0 kg of NMP (N-methylpyrrolidone) and 20.0 mol of Na₂ S.5H₂ Owere charged into a 20-liter polymerization pressure vessel. The mixturewas heated to about 200° C. to distill off water and a small amount ofwater remaining in the vessel: 26 mol). A solution of 20.1 mol ofp-dichlorobenzene in 3.0 kg of NMP was added thereto, and the mixturewas heated at 215° C. for 3 hours. Then, 54 mol of water was addedthereto, and the mixture was heated at 255° C. for 0.5 hour to obtain areaction liquid mixture a, which was taken out and stored. A smallamount of the liquid a was sampled to determine the average degree ofpolymerization of the resulting p-phenylene sulfide prepolymer by thefluorescent X-ray method. The degree of polymerization was 190.

2.2 kg of NMP and 4.0 mol of Na₂ S.5H₂ O was charged into a 20-literpolymerization pressure vessel. The mixture was heated to about 200° C.to distill water and a small amount of NMP (the amount of waterremaining in the vessel: 5.5 mol). A solution of 4.0 mol ofm-dichlorobenzene in 0.6 kg of NMP was added thereto to obtain amixture. 80% of the reaction liquid mixture a obtained as describedabove and 21.0 mol of water were added to the mixture. The mixture wasstirred, and reaction was carried out at 255° C. for 2 hours. Aftercompletion of the reaction, the reaction liquid was diluted about 2times in volume with NMP and filtered. The filter cake was washed withhot water 4 times and dried at 80° C. under reduced pressure to obtain apolymer A [p-phenylene sulfide block copolymer in which the averagedegree of polymerization of the ##STR41## block was 190].

The composition of the polymer A was analyzed by the FT-IR method toreveal that it comprised 82 molar % of the ##STR42## units and 18 molar% of the ##STR43## units. The product had a melt viscosity η* of 690 Pas determined at 310° C. at a shear rate of 200 sec⁻¹, T_(G) of 73° C.and T_(m) of 278° C. After heat treatment at 260° C. for 10 minutes, theproduct had a Ci of 33. T_(G) and T_(m) were measured with adifferential scanning calorimeter.

(2) A liquid reaction mixture b₁ was prepared in the same manner as in(1) and stored. The average degree of polymerization of the p-phenylenesulfide prepolymer in the liquid b₁ was 170.

2.2 kg of NMP and 4.0 mol of Na₂ S.5H₂ O were charged into a 10-literpolymerization pressure vessel. The temperature was elevated to about200° C. to distill off water and a small amount of NMP (the amount ofwater remaining in the vessel: 5.2 mol). A solution comprising 0.7 kg ofNMP and 4.1 mol of m-dichlorobenzene was added thereto. Reaction wascarried out under heating at 215° C. for 3 hours to obtain a liquidreaction mixture b₂. A small amount of the liquid b₂ was sampled todetermine the degree of polymerization of the resulting m-phenylenesulfide prepolymer by fluorescent X-ray method. The degree ofpolymerization was 20.

80% of the liquid b₁ obtained as described above and 20 mol of waterwere charged into a 20-liter polymerization pressure vessel. Reactionwas carried out under heating at 255° C. for 4 hours. After completionof the reaction, a polymer B [p-phenylene sulfide block copolymer havingan average degree of polymerization of ##STR44## block of 180] wasobtained. The polymer B comprised 88 molar % of the ##STR45## units and12 molar % of the ##STR46## units. The product had an Δη* of 580 P,T_(G) of 77° C., Tm of 280° C. and Ci of 35.

(3) 11.0 kg of NMP and 10.0 mol of Na₂ S.5H₂ O were charged into a20-liter polymerization pressure vessel. The mixture was heated to about200° C. to distill off water and a small amount of NMP (the amount ofwater remaining in the vessel: 13 mol). 3.0 kg of NMP, 10.0 mol ofm-dichlorobenzene and 0.10 mol of 1,3,5-trichlorobenzene were addedthereto, and reaction was carried out at 210° C. for 10 hours. 47 mol ofwater was added thereto, and the reaction was carried out at 260° C. for12 hours. After completion of the reaction, a polymer C (m-phenylenesulfide homopolymer) having a η* of about 20 P was obtained.

(4) 11.0 kg of NMP and 20.0 mol of Na₂ S.5H₂ O were charged into a20-liter pressure vessel. The mixture was heated to about 200° C. todistill off water and a small amount of NMP (the amount of waterremaining in the vessel: 26 mol). 3.0 kg of NMP, 20.2 mol ofp-dichlorobenzene and 54 mol of water were added thereto, and themixture was heated at 260° C. for 3 hours to carry out reaction.

After completion of the reaction, a polymer D (p-phenylene sulfidehomopolymer) was obtained in the same manner as in (1). η* was 610 P.

Molding Example C

Each of the phenylene sulfide polymers was mixed homogeneously with aspecific amount of an inorganic filler and a specific amount of anadditive in a Henschel mixer. The mixture was shaped into pellets byextruding with a 30 mm φ unidirectional twin screw extruder at acylinder temperature of 290° to 330° C. The pellets wereinjection-molded in a mold having a transistor vacant frame insertedtherein with an injection-molding machine at a cylinder temperature of300° to 340° C. and mold temperature of 120° to 180° C. under aninjection pressure of 20 to 60 kg/cm². The sealed products were boiledin a red ink for 24 hours, and penetration of the ink through cracks inthe sealing resin or through interfaces between the sealing resin andthe frame was examined. The results are shown in Table C-1.

                                      TABLE Cl                                    __________________________________________________________________________                                             Comp.                                Example No.                                                                              C1    C2    C3    C4    C5    Exam. C                              __________________________________________________________________________    Block copolymer                                                                          A 40 parts                                                                          B 40 parts                                                                          A 25 parts                                                                          A 40 parts                                                                          A 45 parts                                                                          D 40 parts                                                  B 25 parts                                                                          C 10 parts                                                                          D 5 parts                                  Other synthetic              (*5)                                             resin                        5 parts                                          Inorganic filler       (*2)  (*6)  (*6)                                       (fibrous)              10 parts                                                                            15 parts                                                                            15 parts                                                          (*3)                                                                          10 parts                                               Inorganic filler                                                                         (*6)  (*1)  (*1)  (*7)  (*7)  (*1)                                 (non-fibrous)                                                                            60 parts                                                                            60 parts                                                                            29 parts                                                                            25 parts                                                                            33 parts                                                                            60 parts                                                          (*8)                                                                          4 parts                                          Additive               (*4)  (*9)  (*4)                                                              1 part                                                                              1 part                                                                              1 part                                                                        (*10)                                                                         1 part                                     Depth of penetration                                                                     1     1     1     2     2     5                                    of red ink (*9)                                                               __________________________________________________________________________    (*1) silica glass powder: QG-100; a product of Toshiba Ceramic Co., 150       Me**-passed,                                                                  (*2) wollastonite: NYAD G; a product of NYCO Co., 60 Me-passed,               (*3) potassium titanate fibers: TISMO D; a product of Otsuka Kagaku           Yakuhin Co., Japan: 60 Me-passed,                                             (*4) silane: Z 6040; a product of Dow-Corning Co.,                            (*5) epoxy resin: Epikote TM 1009; a product of Shell Petroleum Co.,          (*6) glass fibers: PF-A001, a product of Nittobo Co. (48-100 Me),             (*7) glass beads: CP-2, a product of Toshiba Palodini Co., Japan: 150         Me-passed,                                                                    (*8) mica: A 41; a product of Tsuchiya Kaolin Co., Japan: (0.05 mm),          (*9) titanate: Kr-134S, a product of Kenrich Petrochemicals Co.,              (*10) modified silicone oil: SF 8411; a product of Toray Silicon Co.,         Japan.                                                                        (*11) Depth of penetration of red ink: 1: no penetration, 2:                  substantially no penetration, 3: a little,                                    4: penetration, 5: remarkable.                                                **48Me: opening 0.297 mm, 60Me: opening 0.250 mm, 100Me: 0.149 mm, 150Me:     0.105 mm.                                                                 

What is claimed is:
 1. A printed circuit board comprising an insulatingbase board made of a composite of 50 to 95 vol. % of a polymercomprising mainly a phenylene sulfide block copolymer and 5 to 50 vol. %of a fibrous reinforcing material and a metal layer of a circuit patternformed on the insulating base board, said block copolymer being producedby a process comprising a first step of heating an aprotic polar organicsolvent containing a dihaloaromatic compound consisting essentially of am-dihalobenzene and an alkali metal sulfide to form a reaction liquid(E) containing a m-phenylene sulfide polymer consisting essentially ofrecurring units (B) ##STR47## and a second step of adding ap-dihalobenzene to the reaction liquid (E) and heating the mixture inthe presence of an alkali metal sulfide and an aprotic polar organicsolvent to form a block copolymer consisting essentially of therecurring units (B) and recurring units (A) ##STR48## the reaction inthe first step being carried out until the average degree ofpolymerization of at least 2 and in the range of ##EQU7## wherein Xrepresents a mol fraction of the recurring units (A) in the resultingblock copolymer which is in the range of 0.50 to 0.98 has been obtained;the reaction in the second step being carried out until the mol fraction(X) of the recurring units (A) in the resulting block copolymer hasbecome 0.50 to 0.98; and the reactions in these steps being carried outso that the resulting p-phenylene sulfide block copolymer will have amelt viscosity (η*) measured under conditions of 310° C./200 sec⁻¹ of300 to 50,000 poise and have:(a) a glass transition temperature (Tg) of20° to 80° C., (b) a crystalline melting point (Tm) of 200° to 350° C.,and (c) a crystallization index (Ci) of 15 to 45, this value being thatof the heat-treated, but not stretch-oriented copolymer.
 2. The printedcircuit board according to claim 1 wherein the p-dihalobenzene isp-dichlorobenzene and the m-dihalobenzene is m-dichlorobenzene.
 3. Theprinted circuit board according to claim 1 wherein the alkali metalsulfide is sodium sulfide.
 4. The printed circuit board according toclaim 1 wherein the aprotic polar solvent is an organic amide.
 5. Theprinted circuit board according to claim 4 wherein the amide isN-methylpyrrolidone.
 6. A printed circuit board comprising an insulatingbase board made of a composite of 50 to 95 vol. % of a polymer mainlycomprising a phenylene sulfide block copolymer and 5 to 50 vol. % of afibrous reinforcing material and a metal layer of a circuit patternformed on the insulating base board, said block copolymer being producedby a process which comprises a first step of heating an aprotic polarorganic solvent containing a p-dihalobenzene and an alkali metal sulfideto form a reaction liquid (C) containing a p-phenylene sulfide polymerof recurring units (A) ##STR49## and a second step of adding adihaloaromatic compound consisting essentially of a m-dihalobenzene tothe reaction liquid (C) and heating the mixture in the presence of analkali metal sulfide and an aprotic polar organic solvent to form ablock copolymer consisting essentially of a block consisting essentiallyof recurring units (A) and a block consisting essentially of recurringunits (B) ##STR50## the reaction in the first step being carried outuntil the degree of polymerization of the recurring units (A) has become20 to 5,000 of (A) on the average; the reaction in the second step beingcarried out until the mol fraction (X) of the recurring units (A) in theresulting block copolymer has become 0.50 to 0.98; and the reactions inthese steps being carried out so that the resulting p-phenylene sulfideblock copolymer will have a melt viscosity (η*) measured underconditions of 310° C./200 sec⁻¹ of 300 to 50,000 poise and have:(a) aglass transition temperature (Tg) of 20° to 80° C., (b) a crystallinemelting point (Tm) of 200° to 350° C., and (c) a crystallization index(Ci) of 15 to 45, this value being that of the heat-treated, but notstretch-oriented copolymer.
 7. The printed circuit board according toclaim 6 wherein the p-dihalobenzene is p-dichlorobenzene and them-dihalobenzene is m-dichlorobenzene.
 8. The printed circuit boardaccording to claim 6 wherein the alkali metal sulfide is sodium sulfide.9. The printed circuit board according to claim 6 wherein the aproticpolar solvent is an organic amide.